document.write( "Question 1138452: Simplify the following expressions as much as possible.
\n" ); document.write( "cos(x+y)-cos(x-y)
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Algebra.Com's Answer #756268 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!

\n" ); document.write( "Use these two identities
\n" ); document.write( "\"cos%28x%2By%29+=+cos%28x%29cos%28y%29+-+sin%28x%29sin%28y%29\"
\n" ); document.write( "\"cos%28x-y%29+=+cos%28x%29cos%28y%29+%2B+sin%28x%29sin%28y%29\"\r
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\n" ); document.write( "\n" ); document.write( "to say that,
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\n" ); document.write( "\n" ); document.write( "\"cos%28x%2By%29+-+cos%28x-y%29+=+%280%29+%2B+%28-2sin%28x%29sin%28y%29%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"cos%28x%2By%29+-+cos%28x-y%29+=+-2sin%28x%29sin%28y%29\"\r
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\n" ); document.write( "\n" ); document.write( "The original expression simplifies to -2sin(x)sin(y)\r
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\n" ); document.write( "\n" ); document.write( "\"cos%28x%2By%29+-+cos%28x-y%29+=+-2sin%28x%29sin%28y%29\" is an identity. It is a true equation no matter what values of x and y you select.
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